This invention relates in general to explosive separation apparatus and, more particularly, to explosive separation apparatus having general utility but especially suitable for cutting advanced composite materials used in aerospace vehicles.
Missile staging events are usually initiated with separation systems that employ explosive actuators. One commonly used technique is to use a mild detonating fuse (MDF) to severe the missile skin. The goal of this system is to use the pyrotechnic gas pressure and shock generated by detonation of the MDF to physically break the structure apart at some locally machined groove in the missile skin. However, where structural composites such as graphite-epoxy laminates are employed as in the missile skin, weakening grooves cannot be used. One possible solution is to employ additional metallic structure solely for separation purposes, but this imposes an obvious penalty in weight and complexity.
U.S. Pat. No. 3,971,290 discloses a technique for cutting a composite shell directly using an MDF. A primary problem in the explosive cutting of composite shells is that adjacent structures or materials fracture or delaminate. The adove cited U.S. Patent is not entirely satisfactory in eliminating the delamination in areas adjacent to the separation boundry.
A flexible linear shaped charge (FLSC) has advantages over MDF since the FLSC provides highly directional cutting rather than explosive force in all directions as is the case with an MDF. One advantage in the case of aerospace vehicles is that an FLSC may use less explosive which will reduce the amount of shock imparted to the vehicle during the separation event. However, the installation of an FLSC is a problem since it must be oriented precisely or its reliability is reduced. Heretofore explosive separators employing an FLSC have also produced delamination when used to cut composite materials in an aerospace environment. This delamination can be eliminated if the backward forces of the detonation are not closely confined; however, in most circumstances these backward forces will cause unacceptable damage to adjacent structures if not closely confined.